Here is a list of the game modes we already have but most have not been unlocked from 343i:
There are 3 pages of Game Modes:
****** Page 1 Arena:
Attrition
Attrition Dogeball
CTF
Elimination
FFA Oddball
FFA Slayer
Neutral Flag
Odd Ball
One Flag
Slayer
Strongsholds
****** Page 2:
BTB:CTF
Slayer
Stockpile
Total Control
Fiesta:
Attrition
CTF
One Flag
Slayer
Strongholds
****** Page 3 Ranked:
CTF
Elimination
Odd Ball
One Flag
Slayer
Strongholds
Tactical:
Slayer Commandos
Slayer Manglers
Slayer Sidekicks
Slayer Stalkers Rifles